CN115452724A

CN115452724A - Multi-pass cell assembly and method for monitoring fluid and fluid processing system

Info

Publication number: CN115452724A
Application number: CN202211102777.XA
Authority: CN
Inventors: T·H·鲍姆; J·P·科茨; R·L·赖特二世
Original assignee: Entegris Inc
Current assignee: Entegris Inc
Priority date: 2015-01-19
Filing date: 2016-01-16
Publication date: 2022-12-09
Also published as: US10451540B2; JP6450850B2; CN107250764A; TW201629658A; US20180011003A1; KR101975134B1; KR20170103955A; TWI684082B; WO2016118431A1; JP2018509598A

Abstract

A multipass cell assembly for monitoring fluids is described, as well as fluid processing systems utilizing the multipass cell assembly and associated methods of fluid monitoring using such multipass cell assembly. The multipass cell assemblies are typically used in fluid processing operations such as monitoring vapor deposition process reactants, such as reactants used in vapor deposition metallization of tungsten from a tungsten carbonyl precursor.

Description

Multi-pass cell assembly and method for monitoring fluid and fluid processing system

Divisional application information

The present application is a divisional application of the invention patent application entitled "small volume long path length multipass gas cell for IR and UV monitoring" filed as 2016, 16/1/2016, application No. 201680010504.9.

Cross reference to related applications

The present application claims benefit of priority from U.S. provisional patent application No. 62/105,178 FOR "SMALL VOLUME LONG path length MULTI-PASS GAS CELL FOR IR AND UV MONITORING" (SMALL VOLUME LONG path length MULTI-PASS GAS CELL FOR IR AND UV MONITORING) "filed on 2015, 1, 19, in the name of Thomas h.baum, et al, under the terms of 35u.s.c. 119. The disclosure of this U.S. provisional patent application No. 62/105,178 is hereby incorporated herein in its entirety for all purposes.

Technical Field

The present invention relates to a fluid monitoring apparatus and method that enables small volume, long path length, optoelectronic monitoring of fluids in applications such as the manufacture of semiconductor products, flat panel displays, and solar panels. Optical cells are described that provide increased sensitivity to measurements of fluidic materials, such as liquids and gases within a confined volume. Such optical cells employ multiple reflections from the walls of the optical cavity, and are in particular commonly used for measuring and detecting low concentrations of gases or vapors in a wide range of applications, such as industrial, environmental, public safety, defense, consumer, and medical applications.

Background

Infrared monitoring devices have been developed for use in photodetectors for monitoring fluids (e.g., to quantify or characterize a component of interest in a fluid stream). These devices may be of widely varying types.

In one class of such devices, infrared radiation is passed through a sample cell to interact with a fluid stream flowing through the cell. The infrared radiation source utilized in such devices is typically a broadband infrared light source configured to produce a collimated beam. The beam contacts a fluid stream, which is typically a gas, but may comprise a liquid or a gas/liquid mixture. In this contact, a beam of incident radiation interacts with components of the stream, and the transmitted or reflected signal passes out of the sample cell and strikes the infrared detector.

The infrared detector may be configured in various forms. For example, the infrared detector may comprise a plurality of independent filtering channels, each equipped with a specific filtering element that permits infrared radiation having specific spectral characteristics to pass through. Thus, the separate filtering elements may be used to identify particular components or chemicals of interest that interact with infrared light from the IR light source and produce a distinctive alteration, attenuation, or modulation of such infrared light so that the infrared light output from the sample cell may be identified as being associated with such components or chemicals.

For example, the infrared detector may comprise an IR filter arranged with a receiving thermopile (pyroelectric, etc.) element that converts infrared thermal energy into electrical energy (e.g., DC output signal). Accordingly, a thermopile element associated with a particular filter may be "tuned" to responsively generate an output electrical signal when the thermopile element is illuminated with IR radiation having a particular wavelength or other spectral characteristic dictated by the associated filter.

The infrared fluid monitoring devices described above can be applied to a wide variety of materials and applications. Broadly, the fluid monitoring devices of the present invention may be embodied in any of several variant configurations and forms and may, for example, encompass a wide variety of types of pyroelectric detectors.

As a particular example, a thermopile infrared (TPIR) monitoring system may be employed in a semiconductor fabrication facility in which metallization (e.g., tungsten metallization) is performed by a vapor deposition process using a corresponding metal precursor, with the TPIR monitoring system configured to monitor an effluent stream from the vapor deposition process to detect effluent concentrations of the precursor and its vapor decomposition products produced in the process. The detector utilized in such a TPIR monitoring system may include a reference channel utilized for baseline reference or calibration purposes.

The optoelectronic monitoring system described above must address competing design considerations in use. In general, the path of the infrared beam through the fluid flow in the sample cell desirably has a substantial length that enables corresponding interaction of the incident IR beam with the fluid flow to achieve a high level of accuracy (and resolution) in the detection operation. Thus, a long path length allows achieving a low detection limit. At the same time, in applications where space is expensive and it is desirable to minimize, such as the semiconductor industry, in particular, it is desirable to provide a monitoring system with compact characteristics such that the monitoring system correspondingly has a small volume and a small form factor or footprint.

In addition to infrared light source optoelectronic monitoring systems for detecting and analyzing components of multi-component fluid streams, optoelectronic monitoring systems utilizing other types of light sources, including visible light sources, ultraviolet (UV) light sources, and the like, are also utilized within the art.

Fluid monitoring systems of the type described above require an optical path length having a magnitude suitable for the interaction of particular electromagnetic radiation (e.g., light) with the material being monitored, and as mentioned above, that determines the sensitivity and lower detection limit of measurements that can be achieved by a particular monitoring device. The absorption of electromagnetic radiation is proportional to the path length according to lambert's law or more generally beer-lambert-bragg's law. Path length considerations may limit the practical use of the monitoring device in many applications where low concentration gases or vapors need to be measured. It is not uncommon for path lengths of 1 meter or more to be required to measure materials in concentration ranges as low as a few parts per million, or even parts per billion or lower.

To achieve long path lengths in a sample cell while achieving small-size, small-volume configurations, multi-pass monitoring systems have been proposed and developed. Such small volume, long path length fluid sample cells employ multiple passes or reflections of an incident radiation beam to achieve long path lengths in a relatively small form factor. The small volume allows the time delay to be reduced, while the long path length achieves a lower detection limit.

Thus, the main considerations in achieving a useful photo-fluid monitoring cell are achieving: low sample volume requirements for monitoring operations, extended path lengths for optical monitoring to achieve improved sample measurement sensitivity, efficient optical coupling of components to maximize optical signal utilization, and low cost manufacturability of fluid monitoring cells and associated parts and assemblies.

The art continues to seek improvements in optoelectronic monitoring systems for detecting and analyzing components of multi-component fluid streams, and for real-time fluid stream monitoring.

Disclosure of Invention

The invention relates to a fluid monitoring apparatus and method.

In one aspect, the present invention relates to a multipass cell assembly for monitoring a fluid, the multipass cell assembly comprising:

an arcuate circumscribing member defining a multipass optical reflection chamber, the arcuate circumscribing member comprising an inwardly facing reflective surface along an arcuate extent thereof that produces multipass optical reflection of light impinging thereon;

a light input structure configured to direct light from a light source to the reflective surface of the arcuate circumscribing member such that the multipass optical reflection of light is generated in the optical reflection chamber;

a light output structure configured to direct multi-pass light from the reflective surface of the arcuate circumscribing member out of the optical reflection chamber for detection and processing of the multi-pass light;

a fluid inlet configured to introduce a fluid into the multi-pass optically reflective chamber such that the fluid interacts with multi-pass light in the multi-pass optically reflective chamber; and

a fluid outlet configured to discharge fluid from the multi-pass optically reflective chamber after interacting with multi-pass light in the multi-pass optically reflective chamber.

In another aspect, the present invention relates to a multipass cell assembly for monitoring a fluid, the multipass cell assembly comprising:

a cylindrical wall member circumscribing and defining a multi-pass optical reflection chamber, the cylindrical wall member including circumferentially spaced openings therein;

mirrors in the circumferentially spaced openings, the mirrors facing inward and configured to produce a multipass optical reflection of light in the multipass optical reflection chamber;

a light input structure configured to direct light from a light source onto reflective surfaces of one or more of the mirrors such that the multipass optical reflection of light is generated in the optical reflection chamber;

a light output structure configured to direct multi-pass light out of the optically reflective chamber for detection and processing of the multi-pass light;

a bottom and lid member cooperatively engaging with the cylindrical wall member to enclose the multi-pass optical reflection chamber;

a fluid inlet configured to introduce a fluid into the multi-pass optically reflective chamber such that the fluid interacts with multi-pass light in the multi-pass optically reflective chamber, the fluid inlet comprising at least one fluid inlet port in the bottom piece;

a fluid outlet configured to discharge fluid from the multi-pass optically reflective chamber after interaction with multi-pass light in the multi-pass optically reflective chamber, the fluid outlet comprising at least one fluid outlet port in the bottom piece;

a light source mounted on the cover member and optically coupled to the light input structure; and

a light detector mounted on the cover member and optically coupled to the light output structure.

In yet another aspect, the present invention relates to a fluid treatment system comprising:

a processing tool that utilizes or generates a fluid flow; and

a multipass cell assembly for monitoring fluid as variously described herein is configured for flowing the fluid stream from the fluid inlet through the multipass optically reflective chamber to the fluid outlet for interaction with multipass light in the multipass optically reflective chamber.

Another aspect of the invention relates to a method of monitoring fluid flow, the method comprising: flowing the fluid stream through a multi-pass cell assembly of the present invention as described in various forms herein to produce a multi-pass light output; and processing the multi-pass light output to characterize or analyze the fluid flow.

Other aspects, features and embodiments of the invention will be more fully apparent from the following description and appended claims.

Drawings

FIG. 1 is a simplified schematic top plan view of a multipass cell assembly of the present invention in one embodiment of the invention.

FIG. 2 is a simplified schematic top plan view of a multipass cell assembly of the present invention, according to another embodiment of the invention.

FIG. 3 is a simplified schematic top plan view of a multipass cell assembly of the present invention, according to yet another embodiment of the invention.

FIG. 4 is a simplified schematic top plan view of a multi-pass cell arrangement according to yet another embodiment of the invention.

FIG. 5 is a simplified schematic top plan view of a multipass cell arrangement employing faceted reflective surfaces, according to another embodiment of the present invention.

FIG. 6 is an exploded perspective view of a multipass cell assembly according to yet another embodiment of the invention.

Fig. 7 is a perspective schematic view of a multi-pass pool sub-assembly according to one embodiment of the present invention.

Fig. 8 is a perspective schematic view of a multipass cell assembly including the subassembly of fig. 7.

Fig. 9 is a bottom perspective view of the multipass pool sub-assembly of fig. 7.

Fig. 10 is a schematic elevational view of the multipass pool sub-assembly of fig. 9.

FIG. 11 is a top perspective view of the multipass cell assembly showing details of the gas inlet structure in the multipass cell assembly.

FIG. 12 is a top perspective view of a multipass cell assembly featuring a lid-mounted IR source and IR detector of the cell assembly, according to one embodiment of the invention.

Fig. 13 is an elevational view of the multipass cell assembly of fig. 12.

Fig. 14 is a perspective view of a multi-pass cell assembly of the type shown in fig. 12 and 13, further including a gas flow loop including gas inlet and outlet lines coupled to the multi-pass cell.

FIG. 15 is a perspective view of the multipass cell assembly of FIG. 14, shown with a mass flow controller to indicate a dimension size characteristic of the multipass cell assembly.

FIG. 16 is a graph of output data versus time obtained from a multipass cell assembly monitoring a vapor stream comprising vapor from a vaporizer supplying a tungsten carbonyl precursor vapor and an argon carrier gas, the vapor stream representing a vapor stream for tungsten thin film deposition on a semiconductor substrate in a vapor deposition operation.

FIG. 17 is a schematic representation of a semiconductor manufacturing process system utilizing the multi-pass cell assembly of the present invention in conjunction with a control system for modulating system operation in response to multi-pass cell assembly sensing.

FIG. 18 is a perspective view of a multipass cell assembly according to another embodiment of the invention.

Figures 19 and 20 are perspective views of a 3D printed aluminum composite component of a multipass cell assembly according to one embodiment of the present disclosure, the 3D printed aluminum composite component utilizing a gold coated mirror and configured such that optical alignment is not required after assembly.

Fig. 21 is an elevational view of an infrared source that may be utilized in the multipass cell assembly of fig. 18-20.

Fig. 22 is an elevational view of a 4-channel detector that may be utilized in the multipass cell assembly of fig. 18-20.

FIG. 23 is a bottom plan view of the multipass cell assembly, with gas connections to the cell for transmitting gas into the cell for monitoring operations and for venting monitored gas from the cell. Fig. 24 is a perspective view of such a gas connection with additional gas flow lines.

FIG. 25 is a graph of output data versus time obtained from monitoring, by a linear cell assembly, a vapor stream including vapor from a vaporizer supplying a tungsten carbonyl precursor vapor and a nitrogen carrier gas, the vapor stream representing a vapor stream for tungsten metallization of a semiconductor substrate in a vapor deposition operation.

FIG. 26 is a graph of output data versus time obtained by monitoring a vapor stream comprising vapor from a vaporizer supplying a tungsten carbonyl precursor and a nitrogen carrier gas for a tungsten metallization of a semiconductor substrate in a vapor deposition operation of the invention at operating conditions corresponding to the operating conditions used to generate the data in the graph of FIG. 25.

FIG. 27 is a graph of output data (2 pulses) versus time for a 1m long linear cell assembly monitoring gas flow, including argon at a gas flow rate of 500sccm, at a temperature of 55 ℃ and a pressure of 40 Torr.

FIG. 28 is a corresponding plot of output data (2 pulses) versus time for a multipass cell assembly of the present invention monitoring a gas flow comprising argon carrier gas at a flow rate of 500sccm at a temperature of 55 ℃ and a pressure of 40 Torr.

FIG. 29 is a graph of output data (22 pulses) versus time for a multipass cell assembly of the present invention monitoring a gas flow comprising argon carrier gas at a flow rate of 500sccm at a temperature of 55 ℃ and a pressure of 40 Torr.

FIG. 30 is a graph of output data for tungsten carbonyl precursor vapor versus time in the form of a concentration gradient measurement of a multipass cell assembly of the invention.

Detailed Description

The present invention relates to fluid monitoring apparatus and methods in which extended path optical monitoring of fluids is achieved with a multipass cell assembly having a highly efficient and compact configuration.

an arcuate circumscribing member defining a multi-pass optical reflection chamber, the arcuate circumscribing member comprising an inwardly facing reflective surface along an arcuate extent thereof that produces multi-pass optical reflection of light impinging thereon;

In a particular arrangement of such a multipass cell assembly, the reflective surface can comprise a plurality of mirrors along the arcuate extent of the arcuate circumscribing member. In these arrangements, the arcuate circumscribing member can comprise an arcuate circumscribing support comprising a receiving opening therein in which a respective mirror of the plurality of mirrors is mounted. The mirror may comprise a parabolic mirror or may have other shapes or conformations.

The arcuate circumscribing member in a particular embodiment can comprise a cylindrical wall member, for example, wherein the cylindrical wall member comprises a reflective interior wall surface comprising the inwardly facing reflective surface. Alternatively, the arcuate circumscribing member can comprise a faceted or segmented inner surface comprising the inwardly facing reflective surface.

In various embodiments, the multipass cell assembly can further comprise a cover and a bottom piece cooperatively coupled with the arcuate circumscribing member to enclose the multipass optical reflection chamber.

These cover and base members may include internal reflective surfaces such that the cell itself acts as a light pipe to maximize optical reflection efficiency.

In a particular arrangement, the fluid inlet of the multipass cell assembly can include at least one fluid inlet port in the bottom piece, and the cell assembly in particular embodiments can include two or more such fluid inlet ports to achieve uniformity of the fluid flow through the subassembly.

In a similar manner, the fluid outlet may include at least one fluid outlet port in the bottom piece, and when the bottom piece contains a fluid inlet port, the fluid outlet port may be spaced laterally from the fluid inlet to prevent fluid shorts or other non-uniform or abnormal behavior in the cell assembly.

The light input structure in the multipass cell assembly can comprise a light inlet port configured to accommodate positioning of a light source in the light inlet port or alternatively configured to optically couple to a light source in order to introduce incident light into the multipass optically reflective chamber of the cell assembly.

The light output structure in the multipass cell assembly may similarly comprise a light outlet port configured to accommodate positioning of an output light detector in the light outlet port or alternatively configured to optically couple to an output light detector.

In the multipass cell assembly, the relative positions of the light input port and the light output port with respect to each other are desirably arranged to enable a particular degree of multiple passes of light introduced to the optically reflective chamber, such that the light input and light output of the optically reflective chamber achieve the necessary path lengths for the particular application in which the multipass cell assembly is employed. The relative positions of the respective optical input and optical output ports with respect to each other may vary widely within the broad practice of the present invention.

In some embodiments, it may be desirable to position the optical input port and the optical output port relative to each other to define an included angle therebetween in the range of 30 ° to 90 °. In other embodiments, it may be desirable to position the light input port and the light output port relative to each other to define an included angle therebetween in the range of 35 ° to 75 °. It will be recognized that optimal positioning of the input and output ports can be readily determined within the art based on the disclosure herein to provide a suitable arrangement for a particular implementation of a multipass cell assembly.

The multipass cell assembly can be fabricated from any suitable construction material, and depending on the particular characteristics and composition of the fluid flow flowing through the optically reflective chamber of the multipass cell assembly, can comprise, for example, a metallic material, a ceramic material, an alloy material, a polymeric material, or a composite material, as it is desirable that the construction material of the multipass cell assembly be non-reactive with respect to fluid flow. In some applications, it may be desirable to fabricate the multipass cell assembly, or subassemblies thereof, from materials having high heat capacities in order to facilitate isothermicity in the operation of the cell assembly. The selection of particular materials of construction may be based on the thermal, physical, chemical, and/or optical properties of the materials to achieve a desired performance behavior of the multipass cell assembly. In various embodiments, the arcuate circumscribing member is fabricated from an aluminum composite material to facilitate isothermal operation of the cell assembly in use.

In a particular embodiment, the arcuate circumscribing member of the multipass cell assembly can comprise a molded or micromachined member or a 3D printed member to facilitate economical manufacturing of the cell assembly. More generally, any suitable manufacturing method may be employed.

The mirror (i.e., the reflective surface component of the multipass cell assembly of the present invention) can be of any suitable type suitable for the function and operation of such an assembly in a particular gas monitoring application. In some embodiments, the reflective surface of a multipass cell assembly comprises a plurality of mirrors along the arcuate extent of the arcuate circumscribing member, wherein each mirror comprises a quartz mirror substrate having a gold-coated reflective surface deposited thereon, such as by a vapor deposition technique.

The light input structure of a multipass cell assembly can comprise a light input port in the arcuate circumscribing member of the assembly, and a light source can be disposed in or optically coupled to such light input port. The light source may have any suitable characteristics, and in particular implementations may include an infrared light source, a UV light source, a visible light source, or other light sources having particular desired spectral characteristics. The light source preferably provides collimated light to the optically reflective chamber.

Likewise, the light output structure may include a light output port and the arcuate circumscribing member, and a photodetector may be disposed in or optically coupled to the light output port.

In various particular embodiments, the multipass subassembly can further include a cover and a bottom piece cooperatively engaging the arcuate circumscribing member to enclose the multipass optical reflection chamber. The base member may be integrally formed with the arcuate circumscribing member, or alternatively, the base member may be initially formed as a separate component that is secured to the arcuate circumscribing member, such as by a ridge, a weld, an adhesive bond, a mechanical fastening, or other suitable technique. Likewise, the cover member may be cooperatively engaged with the arcuate circumscribing member in any suitable manner, and may take the form of a detachable cover that is mechanically fastened to the arcuate circumscribing member.

In a particular arrangement, the cell assembly including a lid and a bottom member can further include: a light source mounted on the cover member and optically coupled to the light input structure; and a photodetector mounted on the cover member and optically coupled to the light output structure. This arrangement permits ready access to the light source and light detector sub-assembly for repair, replacement, etc.

In particular embodiments, the light source may comprise an infrared light source and the corresponding light detector may comprise an infrared light detector, e.g., a multi-channel infrared light detector. (the source may be broadband or specific energy band.) this infrared light detector may include appropriate filters and sensing and signal processing components to output one or several appropriate signals for characterizing or analyzing the fluid flow or components thereof in conjunction with passing the fluid flow through the cell assembly.

In various implementations, the multipass cell assembly can include a multipass optical reflection chamber configured to provide a light path length of a particular desired dimensional range, e.g., a light path length in a range of 0.5 meters to 10 meters, or a light path length in a range of 0.5 meters to 5 meters, or a light path length having other dimensional characteristics.

In the multi-pass optical reflection chamber, input light can be directed in and multi-pass light can be directed out of the optical reflection chamber such that the reflected optical path in the chamber has a particular numerical characteristic. The optical path is advantageously non-diametric, i.e. not linearly straight in a straight diametric manner directly from the light input port to the light output port of the optical reflection chamber in a circular optical reflection chamber in which the light path segment has a chordal characteristic such that light impinges on the reflective surface of the arcuate circumscribing member along a continuous optical path for a suitable number of generally continuous reflections.

Thus, in various embodiments, the arcuate circumscribing member can comprise a cylindrical member, and the light input structure and light output structure can be configured to produce the multi-pass optical reflection of light in the optical reflection chamber, wherein the multi-pass optical reflection of light comprises 10-50 non-diametral chordal light reflections in the optical reflection chamber.

In other embodiments, the multipass cell assembly can be configured such that the multipass optical reflection of light comprises from 15 to 40 non-diametric chordal light reflections in the optically reflective chamber. In still other embodiments, the multipass cell assembly can be configured such that the multipass optical reflection of light comprises 18 to 30 non-diametral chordal light reflections in the optically reflective chamber. Any other number of reflections may be employed by appropriately configuring the multipass cell assembly.

a light output structure configured to direct multipass light out of the optically reflective chamber for detection and processing of the multipass light;

a bottom and lid member cooperatively engaged with the cylindrical wall member to enclose the multi-pass optical reflection chamber;

a fluid outlet configured to discharge fluid from the multipass optically reflective chamber after interaction with multipass light in the multipass optically reflective chamber, the fluid outlet comprising at least one fluid outlet port in the bottom piece;

It will be appreciated from the foregoing that the multipass cell assembly of the present invention can be widely varied in structure and operation to achieve efficient multipass optical reflection for extended path length interaction of input radiation with a fluid of interest in the optically reflective chamber.

a processing tool that utilizes or generates a fluid flow; and

a multipass cell assembly for monitoring fluid as described in various forms herein configured for flowing the fluid stream from the fluid inlet through the multipass optically reflective chamber to the fluid outlet for interaction with multipass light in the multipass optically reflective chamber.

The processing tools in such a fluid processing system may be of any suitable type employed for utilizing or generating the fluid flow monitored by the multipass cell assembly.

In one particular embodiment, the processing tool comprises a semiconductor manufacturing tool, such as a vapor deposition tool, configured to deposit a metal (e.g., tungsten) on a semiconductor substrate from a corresponding metal precursor (e.g., a tungsten precursor), and to produce the fluid stream comprising an unreacted precursor (e.g., an unreacted tungsten precursor) or to produce the fluid stream comprising an unreacted tungsten precursor and vapor deposition byproducts of the tungsten precursor resulting from the vapor deposition operation. The metal precursor for this purpose may be of any suitable type, and in various particular embodiments may include a metal carbonyl precursor compound, such as a tungsten carbonyl precursor compound.

Another aspect of the invention relates to a method of monitoring fluid flow, the method comprising: flowing the fluid stream through a multi-pass cell assembly of the present invention as described herein in various forms to produce a multi-pass light output; and processing the multi-pass light output to characterize or analyze the fluid flow.

The light employed in this method may be of any suitable type, and in particular embodiments may include ultraviolet light, visible light, infrared light, or other light having desired spectral characteristics, including combinations of the foregoing spectra. The processing of the multi-pass light output to characterize or analyze the fluid flow may involve any suitable operation effective for this purpose.

For example, the processing may include: the light is filtered and the resulting filtered light is illuminated on a thermopile detection element to analyze the chemical composition of the fluid stream. The fluid streams may include reactants introduced or effluents from semiconductor manufacturing operations, such as vapor deposition including thin film deposition on a semiconductor substrate to deposit at least one of tungsten metal and tungsten nitride on the semiconductor substrate from a precursor vapor of a tungsten carbonyl precursor. The method may be performed, for example, by analyzing chemical concentrations and/or compositions of precursors delivered to or process effluents exhausted from a vapor deposition chamber in order to control one or more process conditions of the semiconductor manufacturing operation and/or to determine an end point for terminating the semiconductor manufacturing operation.

From the foregoing, it will be appreciated that the multipass cell assembly of the present invention can be constructed and implemented in a wide variety of ways to enable monitoring of a wide variety of corresponding fluid flows. The fluid may comprise a gas, which term is to be interpreted broadly as encompassing steam. Alternatively, the fluid may comprise a liquid or a gas/liquid or vapour/liquid multiphase fluid. Additionally, the fluid may include suspended or entrained solids resulting from chemical reactions or decomposition of the fluid occurring in upstream fluid treatment operations, such as particulate contaminants or components in the fluid stream.

Advantages and features of the present invention are further illustrated with reference to the drawings of fig. 1-17 of the present invention.

Referring now to the drawings, FIG. 1 is a simplified schematic top plan view of a multipass cell assembly 100 of the present invention in one embodiment of the invention.

As illustrated, the multipass cell assembly 100 includes a body 317 and an arcuate circumscribing member 200, which can be integrally formed with the body or alternatively separately formed and secured to the body. The arcuate circumscribing member in this embodiment has a cylindrical form, including a cylindrical form of the support wall member 210, defining a multi-pass optical reflection chamber 318 circumscribed by the arcuate circumscribing member 200. The arcuate circumscribing member in this embodiment has a cylindrical nature, but it will be appreciated that in other embodiments, an arcuate circumscribing member extending less than a full circumferential extent around the optical reflection chamber may be employed.

The arcuate circumscribing member as illustrated has a mirror layer 300 on the support wall members 210 to provide an inwardly facing reflective surface 319 along the arcuate extent of the circumscribing member 200. The optically reflective chamber has a diameter 314 that may have any suitable dimensional characteristics suitable for the particular optoelectronic monitoring operation to be performed by the multipass cell assembly.

The multipass cell assembly of fig. 1 includes a light input structure 214 that includes a light input port 220 that can be configured for inputting an input light beam introduced at an input light angle 315 to an optically reflective chamber. As illustrated, an input light beam 332 passes through the optical input port 220 to the inward-facing reflective surface 319 and is thereafter successively reflected to provide a multi-pass (reflected) light beam 336. In this manner, the multi-pass light is output as output beam 330 through the light output structure 216 including the light output port 222. The output light structures can be configured such that light output is transmitted out of the optical reflective chamber at output light angles 316 that are determined by the configuration of the light output structures.

Thus, the arcuate circumscribing member 200 defines a multi-pass optical reflection chamber 318, and the arcuate circumscribing member comprises an inwardly facing reflective surface 319 that produces multi-pass optical reflection of light impinging thereon along its arcuate extent.

The light input structure 214 is configured to direct light from a light source (not shown in fig. 1) onto the reflective surface of the arcuate circumscribing member such that a multi-pass optical reflection of the light is generated in the optical reflection chamber 318. The light output structure is configured to direct the multipass light from the reflective surface of the arcuate circumscribing member 200 out of the optically reflective chamber 318 for detection and processing of the multipass light, such as by passing the multipass light to a photodetector or other optical processing component (not shown in FIG. 1).

The multipass cell assembly 100 of FIG. 1 is additionally provided with suitable fluid inlet and outlet structures (not shown in FIG. 1 for clarity) for: introducing a fluid into a multi-pass optically reflective chamber such that the fluid interacts with multi-pass light in the multi-pass optically reflective chamber, and expelling fluid from the multi-pass optically reflective chamber after interacting with the multi-pass light in the multi-pass optically reflective chamber. Such fluid inlet and outlet structures may be of any suitable type, and may be in the lid of the optically reflective chamber, in the bottom of the optically reflective chamber, through ports in an arcuate circumscribing member, or otherwise provided to enable influencing of fluid ingress and egress for interaction with light in the optically reflective chamber.

The overall effect of multiple reflections in the optically reflective chamber of the multipass cell assembly is to extend the sample path length for increased measurement sensitivity. The path length may be increased or decreased by correspondingly increasing or decreasing the diameter 314 of the optically reflective chamber and/or by increasing or decreasing the number of internal reflections, as determined by the angles of the inlet 315 and output 316 relative to the cell assembly.

Thus, the cell assembly provides a compact and cost-effective design of the gas monitoring cell. The internal path length provided by this design in a particular embodiment may be in the range of 0.5m to 10 m. Path lengths outside this range may be employed, but may be constrained by size and space requirements in a particular application, and depending on the particular spectral region of interest, shorter path lengths may be too small to accommodate particular types of sources and detectors. Longer path lengths may require a pool size and volume that is physically larger than the pool size and volume required in a particular application. Based on the disclosure herein, path lengths within a range suitable for a particular application can be readily determined by modeling or empirical testing. In various embodiments, a path length of 0.5m to 5m may be employed to achieve appropriate sensitivity with compact size and internal sample volume. The sample volume (i.e., the volume of the optical reflection chamber) in various embodiments may range from 10mL to 200mL, although sample volumes less than or greater than this range of sample volumes may generally be employed in other embodiments.

The cell assembly shown in fig. 1 may be constructed from a suitable block of material constituting a body 317 in which a cavity having a circular cross-sectional section is cut to form an optically reflective chamber 318. The block may be formed of any suitable construction material (e.g., metal, ceramic, polymer, compound of materials, etc.). In a particular embodiment, a surface of a wall bounding such a circular cross-section optically reflective chamber can be polished to a mirror quality finish to provide an inwardly facing reflective surface 319. Top and bottom plates may be added to provide a circular cross-sectional area cavity bounded by the top and bottom plates and by the arcuate circumscribing member 200 having the mirror layer 300 thereon, which as indicated, may be a layer of integrally formed wall members 210. The top and bottom plates may also be mirror polished to provide a cavity that functions as a light pipe and generates the multiple reflections needed to produce an extended optical path length.

Various configurations of the multipass cell assembly are possible with respect to the placement and positioning of the light input structure and the light output structure.

FIG. 2 is a simplified schematic top plan view of a multipass cell assembly of the present invention, according to another embodiment of the invention. Reference numerals for corresponding parts and elements of the multipass cell assembly of fig. 2 are correspondingly numbered with respect to the same parts and elements of fig. 1. The multipass cell assembly of FIG. 1 includes input and

output light structures

214 and 216, respectively, that are circumferentially spaced apart from one another, such as at an angle of 60-75. In contrast, the input and

output light structures

214, 216 in the multi-pass light assembly of FIG. 2 are positioned in close proximity to one another, i.e., circumferentially spaced at an angle that may be about 30-45.

FIG. 3 is a simplified schematic top plan view of a multipass cell assembly of the present invention, portions and elements of which are correspondingly numbered with respect to those of FIG. 1, according to yet another embodiment of the invention. In the multipass cell assembly of fig. 3, the light input and output structures are also in close proximity, with the light input structure 214 having an associated light input pathway that intersects the light output pathway of the light output structure 216.

Fig. 4 is a simplified schematic top plan view of a multipass cell arrangement, portions and elements of which are numbered correspondingly with respect to those of fig. 1, according to yet another embodiment of the invention. In the multipass cell assembly of fig. 4, a light source element 340 is positioned in the light input port 220 of the light input structure 214, and a light detector element 342 is disposed in the light output port 222 of the light output structure 216. In a specific implementation of this embodiment, 20 multipaths of a reflection may be generated to provide a path length of 1 m.

Fig. 5 is a simplified schematic top plan view of a multi-pass cell arrangement employing faceted reflective surfaces, corresponding portions and elements in the multi-pass cell arrangement being correspondingly numbered with respect to those of fig. 1, in accordance with another embodiment of the present invention. In this embodiment, the inwardly facing reflective surface 319 bounding the optically reflective chamber 318 is comprised of a faceted wall surface, and employs the light source 340 and the light detector 342. As an illustrative example, such a system in a particular embodiment may be configured to provide 21 reflections in an optical reflection chamber, resulting in a corresponding path length of 1.03 m.

In the foregoing embodiments of fig. 1-5, the number of reflections from the wall surfaces of the optically reflective chamber is controlled by the angle used for the input source radiation. The overall path length of the cell is determined by the number of reflections times the diameter of the internal cavity, and the height of the internal cavity is set to be compatible with the size of the source radiation and the geometry of the radiation beam as it exits the cell. In a particular embodiment, the beam geometry may be adapted to interface to a particular type of instrument by providing secondary optics, including a focusing lens.

The overall size of the multipass cell assembly can vary widely. In some embodiments, the cell can be micromachined to provide a miniaturized or small scale gas sampling system. In such cases, a light source assembly that produces a highly collimated micro cross-sectional beam having a micron or sub-micron size will be employed. The multipass cell assembly in various implementations can be used in spectroscopic gas measurement systems on integrated circuit chips or otherwise for small scale or nanoscale implementations.

FIG. 6 is an exploded perspective view of a multipass cell assembly according to yet another embodiment of the invention. In the multipass cell assembly of fig. 6, portions and elements corresponding to those illustratively described in fig. 1-5 are numbered correspondingly.

The assembly of fig. 6 includes a cavity 317 characterized by a plated mirror surface 319 circumscribing an optical reflection chamber. The chamber is also circumscribed by an O-ring seal element 721 to achieve a leak-proof seal of the optical reflective cavity with the top cover 402. A similar O-ring sealing element (not shown in fig. 6) is provided at the bottom portion of the chamber for leak-proof sealing of the optical reflective cavity with a bottom cover 404.

Cavity 317 is provided with longitudinally elongated mechanical fastener openings to accommodate

shoulder bolts

410, 412 and 414 that secure top cover 402 in place and

shoulder bolts

416 and 418 that secure bottom cover 404 in place. The block is provided with an entrance port 220 that accommodates light input from an input light source (not shown in fig. 6), and also includes a light output port 222 that accommodates light output to a light detector (not shown in fig. 6).

The top cover 402 of the multipass cell assembly of FIG. 6 is provided with a polished plated surface 720, and the bottom cover 404 is likewise provided with a polished plated surface 728, to enhance the optical reflective properties of the optical reflective cavity bounded by the top and bottom covers and the plated mirror surface 319 of the optical reflective cavity.

In the assembly of fig. 6, a fluid inlet 406 and a fluid outlet 408 are provided in the top cover to provide for the introduction of fluid into the optically reflective chamber in the inlet 406 for interaction with light in the optically reflective chamber, and for the evacuation of fluid after the fluid interacts with the multipass light in the optically reflective chamber in the outlet 408.

The multipass cell assemblies of the present disclosure can be used to measure and/or characterize gases and vapors, as well as other fluids, including liquid and liquid/gas and liquid/vapor materials, as well as solid/vapor materials. The spectral region of light interacting with the fluid may be within any suitable range of wavelengths in the electromagnetic radiation spectrum or may be a specific wavelength. In particular applications, the light used to measure and/or characterize a fluid may be ultraviolet light, visible light, near-infrared light, mid-infrared light, or other particular spectral systems or wavelength ranges, including mixtures of different types of radiation used to detect or characterize a particular material (e.g., a fluid or a fluid component).

The applications covered by the multi-pass subassembly of the present invention are of a widely varying type. For example, this type of assembly can be used to measure low levels of chromophores in the UV and visible spectral regions, including detecting and monitoring low concentrations of organic materials in water samples. The liquid composition can be monitored by short wave near infrared measurement using path lengths, which can be, for example, about 5cm to 20cm or more.

The optical reflective chamber of the assembly can be used to measure low level fluorescence, phosphorescence or chemiluminescence with longitudinal excitation down the axis of the cell. In liquid applications, the optically reflective chamber may be configured, for example, as a polished metal wall cavity for applications in which the fluid of interest does not contaminate, or erode the metallic material. In applications utilizing fluids with potential interaction with metallic build materials, the optically reflective chamber can be formed of a polymer, glass, or quartz material, or can be coated with a reflective surface material on the exterior walls of the cell to provide suitable reflectivity while protecting the underlying metal from corrosion.

The optically reflective chamber may be configured as a cylindrical chamber or as a tubular chamber, or the optically reflective chamber may be configured in other ways suitable for a particular application, thereby accommodating multi-pass operation of the chamber to achieve an extended path length for monitoring a particular fluid.

Thus, the multipass cell assembly of the present invention can be used to interact fluids with light (involving absorption) as well as for other forms of optical spectroscopy. The cell assembly may utilize a cavity formed with a polished generally vertically extending surface and formed with its top and bottom sealed by a flat polished surface to form an overall reflective cavity. Light can be introduced into the cavity through a circular cross-section aperture in the vertically extending surface such that the light is directed across the cavity to the opposing surface with an angle of incidence such that the light reflects from the wall at an angle different from that of the incoming light beam to initiate a sustained path of multiple reflections from the enclosed vertically reflective surface of the cavity, with the light ultimately exiting the cavity from a second aperture in the vertically extending surface. The light/radiation interacts with the fluid sample during multiple reflections within the cavity, and the effective path length is determined by the total number of inter-wall reflections within the cavity and the distance traveled between successive reflections, which in turn is determined by the distance between opposing surfaces within the cavity and the input and exit angles of the respective light/radiation input and output apertures.

The cavity may be provided in the form of a circular cross-section chamber constituting an internal reflective region defined by a cylindrical circumscribing surface from which light/radiation is reflected. As indicated above, the cavity may be enclosed by a continuous planar reflective surface, such as a plate at the respective top and bottom ends of the cell cavity.

The respective apertures for the light source and light detector components may be machined or drilled into the walls of the cell to provide respective circular cross-section openings to accommodate the respective light source and detector devices, or alternatively mirrors, fiber arrays, or other components may be employed that optically couple the light inlet and outlet apertures with the respective source and detector devices. The aperture may have appropriate dimensional characteristics to define an initial diameter of the light beam input to or output from the optically reflective cavity. The diameters of the optical input and output beams may be the same or different from each other depending on the degree of divergence or convergence of the beams within the cell.

The nominal or average path length of the pool is determined by: the relative angle between the input and output apertures in the walls of the cell along the horizontal plane relative to the base of the cell, and the diameter across the cylindrical cross-sectional section of the cell. The parallelism of the opposing wall surfaces in the cavity is used to ensure optimal reflection geometry within the cell. The top and bottom reflective interior surfaces of the components enclosing the cell help correct for vertical deviation of the beam and form light pipe-like structures in the cell.

The cell may be provided with two or more ports for input and output of materials (e.g., gases, vapors, liquids, etc.) being monitored in the cell. The ports may be located in the top and/or bottom plates (or in the sidewalls), such as openings that may be machined in such structural components of the cell. The fluid-tight nature of the optically reflective cavity can be achieved with a continuous seal (e.g., provided by an O-ring of a suitable elastomeric composition) or other form of mechanical seal. For example, a groove or recess may be cut in the body portion of the well to accommodate this type of O-ring for sealing the cavity bounded by such top and bottom plates. A seal of suitable character may be employed to support vacuum, atmospheric or super-atmospheric pressure of the fluid in the cell.

The circumscribing wall of the optically reflective cavity can comprise a machined or molded continuous surface defining a circular cross-section of the cavity. Alternatively, the reflective wall surfaces may be faceted, segmented, or otherwise shaped to provide suitable reflective (/ focusing) surfaces for multipass light transmission in the cavity. The surface may be machined or otherwise configured to provide an appropriate degree of divergence or convergence of the reflected beam. The light input structure may be configured such that incoming light strikes the center of a relatively facing region of the circumscribing wall such that the beam undergoes multiple internal reflections between the facets of the faceted wall until the beam exits as reflections from the facet surfaces through the exit aperture of the output structure.

The light input structure may be configured to provide a collimated beam of radiation to the optically reflective cavity, wherein a characteristic of the outgoing beam is collimated or nearly collimated, depending on the geometry of the inner reflective wall surface. The cell may be employed with any suitable detection/analysis instrument, such as photometers, spectrophotometers, and other optical analyzers. If necessary or desired, the multi-pass beam exiting the optical reflective cavity can be processed with appropriate imaging optics for transmission to the detector system of the instrument or to a photometric or spectroscopic equivalent of the detector system.

Suitable source and detector devices can be tightly coupled to the multipass cell without the need for any external focusing optics to make up a fully integrated fluid monitoring system. The source device may be disposed adjacent to or within the light/radiation input aperture. In a similar manner, a light/radiation detector may be disposed adjacent to or within the light/radiation output aperture. The respective light/radiation input and output apertures may be provided with windows to provide a suitable seal for the optically reflective cavity. The window used for this purpose may be constructed of a suitable material that is rigid, inert to the sample being monitored and to the surrounding operating environment, and transparent in the spectral region of interest. Coatings may be employed on either or both sides of the window to enhance chemical inertness and/or reduce reflection losses at either optical surface. The window may be held in place by mechanical sealing elements (e.g., O-rings or equivalents), sealants, adhesive joining media, brazing or other joining or securing techniques and materials.

The cell may be made of any suitable construction material depending on the physical and chemical requirements of the monitoring application, the chemical reactivity of the fluid medium, regulatory requirements, operating environment, cost considerations, and the like. For example, the cell may be made of a metal (e.g., aluminum, stainless steel, or a special alloy required to meet applicable standards for chemical inertness). The optical surfaces of the internal cavity may be provided by suitable polishing and/or cutting procedures, such as diamond turning. The reflectivity of the cut/polished surface can be enhanced by depositing a reflective material, such as gold, nickel, dielectric material, etc.

The pool may also be formed of metal or other suitable construction material by casting or molding techniques, wherein the optical surfaces are polished. Materials of construction such as ceramics, engineered polymers, or other polymers or resins (thermoplastic, thermoset, or catalytically cured) are contemplated, with the reflectivity of the optical surface optionally enhanced by deposition of a reflective metallic or dielectric material. The pool cavity walls may be formed by molding, casting or other techniques into segments for subsequent assembly of a composite wall structure, which may be faceted or otherwise shaped or contoured to achieve suitable reflective properties in use of the pool. The wall segments in such composite wall structures may be assembled in a joined manner by a suitable adhesive or sealant material.

The cell may be fabricated from a thermally conductive material and incorporate heat transfer components or capabilities such that the interaction of light/radiation with the fluid in the cell occurs at a particular temperature. For this purpose, the cell may be fabricated so as to ensure isothermal operation, where the temperature of the cavity is nearly uniform throughout the optical reflection chamber. For this purpose, heater elements or heat transfer passages may be provided in the chamber wall and/or the cover component.

Fig. 7 is a perspective schematic view of a multi-pass pool sub-assembly according to another embodiment of the present invention. This pool subassembly includes a bottom mounting flange 420 from which the arcuate circumscribing member 200 extends upwardly in the form of a cylindrical wall with a light input port 220 configured therein, as shown.

The cylindrical wall includes therein a series of receiving openings 422 along the circumferential extent of the wall intermediate the upper and lower ends of the wall, the receiving openings including a light input port opening and a light output port opening. In the receiving opening, the remaining openings, except for the openings for the light input port and the light output port, are provided with mirrors 424 for generating a reflective path for radiation impinging thereon. An O-ring receiving groove 426 is provided at an upper end of the cylindrical wall to receive an O-ring inserted therein for sealing the optical reflection chamber.

Fig. 8 is a perspective schematic view of a multipass cell assembly including the subassembly of fig. 7. The multipass cell assembly 100 includes a light input structure 214 and associated light source 106 and light detector 108. The cell assembly includes a housing 102 and a cover member 104.

Fig. 9 is a bottom perspective view of the multipass pool sub-assembly of fig. 7, showing the bottom mounting flange 420, receiving opening 422, and mirror 424.

Fig. 10 is a schematic elevational view of the multipass pool sub-assembly of fig. 9. As illustrated, the light source 106 is arranged in relation to the light input structure to introduce an input light beam into the optically reflective chamber. The receiving opening 422 of the cell sub-assembly is illustrated along with the light output structure 216, which receives the output beam from the optical reflection chamber and directs this beam to the detector of the assembly.

Fig. 11 is a top perspective view of a multipass cell assembly showing details of a fluid inlet structure in the multipass cell assembly. As illustrated, the arcuate circumscribing member 200 circumscribes an optically reflective chamber 318 in the cell assembly housing 102, and the fluid inlet (/ outlet) port 110 is provided for introducing fluid into the optically reflective chamber for flow therethrough.

FIG. 12 is a top perspective view of a multipass cell assembly featuring a cell assembly including a lid-mounted IR source and a lid-mounted IR detector, according to one embodiment of the invention.

The cell assembly cover member 104 shown in fig. 12 has mounted thereon a light source 106 and a light detector 108, with an electronics module 112 therebetween, for performing monitoring operations and generating monitoring output signals.

Fig. 13 is an elevational view of the multipass cell assembly of fig. 12. As illustrated, the cell assembly housing 102 engages the cell assembly cover member 104, and the cover member 104 has mounted thereon a light source 106, a light detector 108, and an associated electronics module 112.

Fig. 14 is a perspective view of a multi-pass cell assembly of the type shown in fig. 12 and 13, further including a gas flow circuit including gas inlet and outlet lines coupled to the multi-pass cell. The gas flow circuit includes a gas inlet line 114 manifolded to introduce fluid through the bottom of an optically reflective chamber within the cell assembly housing 102 via spaced apart fluid inlet ports in the bottom of the chamber. A gas outlet line 116 is provided for exhausting the fluid from the optically reflective chamber after the fluid interacts with the multipass light in the optically reflective chamber.

Fig. 15 is a perspective view of the multipass cell assembly 100 of fig. 14, shown with mass flow controllers 120 to indicate the relative size characteristics of the multipass cell assembly.

FIG. 16 is a graph of output data versus time obtained from a multipass cell assembly monitoring vapor flow including vapor from a vaporizer supplying tungsten carbonyl precursor vapor and a nitrogen carrier gas, the vapor flow representing a vapor flow for tungsten metallization of a semiconductor substrate in a vapor deposition operation.

The vaporizer used to generate the data of fig. 16 was operated in a pulse flow format at a temperature of 55 ℃ and a pressure of 40 torr to deliver tungsten carbonyl precursor vapor in a combined argon/nitrogen carrier gas flow at an argon carrier gas flow rate of 500 seem and a nitrogen carrier gas flow rate of 50 seem. In accordance with the present invention, an integrated vapor comprising a carrier gas and a tungsten carbonyl precursor vapor is flowed to a multi-pass cell assembly, wherein the multi-pass cell assembly comprises a 4-channel infrared detector. The radiation input to the optically reflective chamber of the cell assembly is infrared radiation.

The first channel for monitoring carbon monoxide (CO) in the four-channel detector is composed of blue line

Indicating, monitoring carbon dioxide (CO) ₂ ) The second channel of (2) is composed of magenta lines

Indicating, monitoring the third channel of the tungsten carbonyl precursor by the green line

Indicated, and the fourth channel is the reference channel, indicated by the red line

And (4) indicating.

The data of the graph of FIG. 16 indicates that the multipass cell assembly is characterizing the gas flow with respect to CO, CO ₂ And tungsten carbonyl compounds and is highly effective in demonstrating the quality of performance of the vaporizer in providing tungsten carbonyl precursor vapor.

The multi-pass cell assembly 100 is located downstream of the vapor deposition tool 124 (or alternatively, the multi-pass cell assembly may be located upstream of the vapor deposition tool), which may comprise, for example, a chemical vapor deposition process chamber disposed in a semiconductor manufacturing facility.

The vapor deposition tool 124 in this process system is arranged to receive precursor vapor from a precursor source vessel 126 and carrier gas from a carrier gas source vessel 128. The respective precursor and carrier gas flows combine to form a precursor gas mixture that flows along a precursor gas mixture feed line 130 to the vapor deposition tool. The vapor deposition process conducted in the vapor deposition tool 124 produces effluent that is discharged from the tool along effluent discharge line 134 and passed to the multipass cell assembly 100. The effluent gas is monitored in the multipass cell assembly and is discharged from this assembly as a final effluent along a discharge line 136.

The multipass cell assembly 100 monitors the effluent gas and generates a corresponding output, which is transmitted along output signal transmission line 138 to a Central Processor Unit (CPU) 132.CPU 132 may be programmably arranged to process the output signals from output signal transmission lines 138 and responsively generate the associated control signals, which are output along control signal transmission lines 140 and control signal transmission lines 142. In this arrangement, the control signals in line 140 are used to modulate the operation of the vapor deposition tool 124, and the control signals in line 142 are used to modulate the supply of precursor and carrier gases from the respective precursor vessels 126 and carrier gas vessels 128.

With this arrangement, process conditions in the vapor deposition tool 124 or associated with the vapor deposition tool 124 may be controllably adjusted to maximize deposition of tungsten on substrates metallized in the tool while avoiding undesirable side reactions of the precursor vapor that may otherwise produce undesirable levels of solid particles or other contaminants. The control signals in signal transmission line 142 may correspondingly be used to adjust the concentration of precursor in the precursor gas mixture flowing along line 130 to the tool, e.g., by modulating flow control valves associated with

vessels

126 and 128, to thereby achieve a desired concentration of precursor in the precursor gas mixture.

The multi-pass cell assembly may be used, in addition to process control purposes, to detect the end point of a process operation or a near-depleted condition of a supply vessel containing precursor and carrier gases, and correspondingly terminate the operation of the process. The CPU 132 for this purpose may comprise any suitable processor component and configuration, and may, for example, comprise a dedicated processor programmed for monitoring and controlling a process system utilizing a multipass cell assembly. Alternatively, the CPU may include a microprocessor, programmable logic controller, or other controller component.

From the foregoing, it will be appreciated that the multipass cell assemblies of the present invention are generally useful in a wide variety of fluid monitoring operations and applications to enable extended path length radiation-based monitoring of fluids and materials containing fluids, and that the multipass cell assemblies, due to the structural arrangements described herein, can be deployed in an extremely compact form as desired in applications such as semiconductor manufacturing, in which the footprint and volume of process components are desirably minimized. It will also be apparent from the foregoing discussion that the multipass cell assembly of the present invention is of a relatively simple form and is suitable for cost-effective manufacture, assembly, installation and operation.

The multipass cell assembly of the present invention advantageously can be used in various embodiments to monitor selected gas components of a gas utilization equipped process stream supplied into a process system. An example is the use of such a multipass cell assembly to monitor tungsten hexacarbonyl W (CO) in a process gas stream supplied to a vapor deposition tool in a manufacturing process system for depositing tungsten on a substrate ₆ . The vapor deposition tool in such an application may, for example, comprise a Chemical Vapor Deposition (CVD) process tool or an Atomic Layer Deposition (ALD) process tool. The manufacturing process system comprising the multipass cell assembly of the present invention can be used to produce semiconductor products, flat panel displays, solar panels, or other products.

In such applications, a multipass cell assembly including an arcuate circumscribing member defining a multipass optical reflective chamber can be used to improve the signal-to-noise characteristics of a monitoring signal related to a corresponding linear monitoring cell assembly without a perceptible reduction in overall signal strength (even though the circular geometry provides an increased optical surface as compared to a linear cell assembly).

In another embodiment, the multipass cell assembly of the present invention may be configured within a housing as shown in fig. 18, coupled by a power cable to a suitable source of electrical energy, and having a USB cable attached to the cell for transmission of monitoring signal data to an associated processor, which may comprise a microprocessor, programmable logic device, dedicated programmable computer, or the like, configured to process the monitoring signal data and provide a corresponding output, e.g., an output for the purpose of monitoring and controlling gas supply equipment for supplying the monitored gas. The gas supply equipment may, for example, comprise precursor vapors generated by: the corresponding vaporizer vessel containing the solid precursor is heated such that the solid precursor volatilizes to form a corresponding precursor vapor for delivery to a downstream processing tool. The multipass cell assembly in this case may be equipped with a heater jacket to prevent condensation or solidification of the precursor vapor or components thereof, so that the monitoring operation is carried out in an efficient manner.

A multipass cell assembly of the type as shown in fig. 18 may be configured with a suitable beam source, such as an infrared source, that generates pulses at an appropriate frequency and is otherwise constructed to provide an appropriate signal-to-noise ratio in operation. In a particular embodiment, the pulse frequency is 10Hz. The multipass cell assembly is constructed and arranged to reduce thermal drift and minimize extraneous noise, and provide an appropriate fast response time with low thermal drift, small footprint, and modular design.

Fig. 21 is an elevational view of an infrared source that may be utilized in conjunction with the multipass cell assembly described in fig. 18-20. As indicated, the infrared source may be pulsed at a suitable frequency (e.g., 10 Hz), have a compact design, and exhibit low power consumption.

Fig. 22 is an elevational view of a 4-channel detector that may be utilized in the multipass cell assembly described in connection with fig. 18-20. The detectors may be provided in a compact "four" board configuration as shown, the detectors being constructed to exhibit suitable low temperature sensitivity and noise sensitivity characteristics.

FIG. 23 is a bottom plan view of the multipass cell assembly described above, with gas connections to the cell for transmitting gas into the cell for monitoring operations and for venting monitored gas from the cell shown. Fig. 24 is a perspective view of such a gas connection with additional gas flow lines.

The monitoring data of fig. 25 was generated at a temperature of 55 ℃ and a pressure of 40 torr for a gas flow comprising tungsten carbonyl precursor vapor in a combined argon/nitrogen carrier gas flow at an argon carrier gas flow rate of 500 seem and a nitrogen carrier gas flow rate of 50 seem. A composite vapor comprising a carrier gas and a tungsten carbonyl precursor vapor is flowed to a linear cell assembly, and the assembly comprises a 4-channel infrared detector. The radiation input to the linear cell assembly is infrared radiation.

Indicating that the third channel for monitoring the tungsten carbonyl precursor is covered by a green line

And (4) indicating.

FIG. 26 is a graph of output data versus time obtained by monitoring a vapor stream comprising vapor from a vaporizer supplying a tungsten carbonyl precursor and a nitrogen carrier gas at operating conditions corresponding to the operating conditions used to generate the data in the graph of FIG. 25 for a multi-pass cell assembly of the present invention, the vapor stream representing a vapor stream for tungsten metallization of a semiconductor substrate in a vapor deposition operation.

Thus, the monitoring data of fig. 26 was also generated at a temperature of 55 ℃ and a pressure of 40 torr for a gas flow comprising a tungsten carbonyl precursor vapor in a combined argon/nitrogen carrier gas flow at an argon carrier gas flow rate of 500 seem and a nitrogen carrier gas flow rate of 50 seem. The integrated vapor comprising the carrier gas and tungsten carbonyl precursor vapor flows to the multi-pass cell assembly of the present invention, and the assembly comprises a 4-channel infrared detector. The radiation input to the multipass cell assembly is infrared radiation.

The first channel in a four-channel detector associated with a multipass cell assembly for monitoring carbon monoxide (CO) is represented by the blue line

And (4) indicating.

Comparison of the data in the graph of FIG. 25 for a linear cell assembly with the data in the graph of FIG. 26 for a multipass cell assembly of the present invention indicates that the multipass cell assembly is monitoringMeasuring the relation of gas flow to CO, CO ₂ And a tungsten carbonyl compound are highly effective in terms of composition. No volume retention or coagulation was noted in the multipass cell assembly.

FIG. 27 is a graph of output data (2 pulses) versus time for a 1m long linear cell assembly monitoring gas flow, including argon at a gas flow rate of 500sccm, at a temperature of 55 ℃ and a pressure of 40 Torr. The monitoring system includes a linear cell assembly including a 4-channel infrared detector. The radiation input to the linear cell assembly is infrared radiation. The pulsed operation included a pulse "on" for a 1m long linear cell duration of 5 seconds and a pulse "off" for a duration of 10 seconds, with data collection at a rate of 4 Hz.

FIG. 28 is a corresponding plot of output data (2 pulses) versus time for a multipass cell assembly of the present invention monitoring a gas flow comprising argon carrier gas at a flow rate of 500sccm at a temperature of 55 ℃ and a pressure of 40 Torr. The monitoring system includes a multipass cell assembly including a 4-channel infrared detector. The radiation input to the multipass cell assembly is infrared radiation. Pulsed operation included pulse "on" for a 5 second duration and pulse "off" for a 10 second duration of the multipass cell, with data collection at a rate of 10Hz. Comparison of fig. 27 and 28 shows that the multi-pass cell assembly of the present invention provides a faster overall response, is more informative, and has a visible pulse shape than a linear monitoring cell assembly.

FIG. 29 is a graph of output data (22 pulses) versus time for a multipass cell assembly of the present invention monitoring a gas flow comprising argon carrier gas at a flow rate of 500sccm at a temperature of 55 ℃ and a pressure of 40 Torr. The pulsed operation of the multipass cell included a pulse "on" of 5 seconds duration and a pulse "off" of 10 seconds duration, with data collection occurring at a rate of 10Hz.

FIG. 30 is a graph of output data for tungsten carbonyl precursor vapor versus time in the form of a concentration gradient measurement of a multipass cell assembly of the invention. The tungsten carbonyl precursor stream was at a temperature of 55 c and at a pressure of 40 torr with a nitrogen carrier gas flow rate of 50 sccm. The performance of the multipass cell assembly remained the same over time for 6 replicates.

In summary, the multipass cell assemblies of the present invention exhibit general performance trends consistent with linear cell assemblies, and exhibit advantages over linear cell assemblies in improved behavior with respect to temperature fluctuations, improved behavior with respect to electronic noise, and faster signal response times, with no observed retention.

------------

Although the present invention has been described herein with reference to particular aspects, features and illustrative embodiments, it will be appreciated that the utility of the present invention is not limited thereto, but extends to and encompasses numerous other variations, modifications and alternative embodiments, as will occur to those of skill in the art to which the invention pertains based on the description herein. Accordingly, the invention as hereinafter claimed is intended to be broadly construed and interpreted, as including all such variations, modifications and alternative embodiments, within its spirit and scope.

Claims

1. A multipass cell assembly for monitoring a fluid, comprising:

an arcuate circumscribing member defining a multi-pass optical reflection chamber, the arcuate circumscribing member comprising an inwardly facing reflective outer surface along an arcuate extent thereof that produces multi-pass optical reflection of light impinging thereon, wherein the arcuate circumscribing member is transparent and chemically resistant;

a light input structure configured to direct light from a light source onto the reflective outer surface of the arcuate circumscribing member such that the multipass optical reflection of light is generated in the optical reflection chamber;

a light output structure configured to direct multi-pass light from the reflective outer surface of the arcuate circumscribing member out of the optical reflection chamber for detection and processing of the multi-pass light;

2. The multipass cell assembly of claim 1, wherein the arcuate circumscribing member comprises a faceted or segmented inner surface comprising the inwardly facing reflective outer surface.

3. The multipass cell assembly of claim 1, further comprising a cover and bottom piece cooperatively engaged with the arcuate circumscribing member to enclose the multipass optical reflection chamber.

4. The multipass cell assembly of claim 1, wherein the light input structure comprises a light input port, and wherein the light output structure comprises a light output port, wherein the light input port and the light output port define an included angle therebetween in the range of 30 ° to 90 °.

5. The multipass cell assembly of claim 1, further comprising a cover and bottom member cooperatively engaged with the arcuate circumscribing member to enclose the multipass optical reflection chamber, further comprising a light source mounted on the cover member and optically coupled to the light input structure, and further comprising a light detector mounted on the cover member and optically coupled to the light output structure.

6. The multipass cell assembly of claim 1, wherein the multipass optical reflection chamber is configured to provide an optical path length ranging from 0.5 meters to 10 meters.

7. The multipass cell assembly of claim 1, wherein the arcuate circumscribing member comprises a cylindrical member, and the light input structure and light output structure are configured to produce the multipass optical reflection of light in the optical reflection chamber, wherein the multipass optical reflection of light comprises 10-50 non-diametral chordal light reflections in the optical reflection chamber.

8. A multipass cell assembly for monitoring a fluid, comprising:

a light input structure configured to direct light from a light source onto a reflective surface of one or more of the mirrors such that the multipass optical reflection of light is generated in the optical reflection chamber;

9. A fluid treatment system, comprising:

a processing tool that utilizes or generates a fluid flow; and

the multipass cell assembly for monitoring fluid of any one of claims 1-8, configured for flowing the fluid stream from the fluid inlet through the multipass optically reflective chamber to the fluid outlet so as to interact with multipass light in the multipass optically reflective chamber.

10. The fluid processing system of claim 9, wherein the processing tool comprises a vapor deposition tool, wherein the vapor deposition tool is configured to deposit tungsten on a semiconductor substrate from a tungsten precursor and generate the fluid stream comprising an unreacted tungsten precursor.

11. A method of monitoring fluid flow, comprising: flowing the fluid stream through the multipass cell assembly of any one of claims 1-8 to produce a multipass light output; and detecting and processing the multi-pass light output to characterize or analyze the fluid flow.